Coupling signal processing circuitry with a wireline communications medium

ABSTRACT

A system and method for processing a communication signal from a wireline is provided. The system comprises a coupling unit and signal processing circuitry. The coupling unit comprises at least one transformer and is configured to receive the communication signal from the wireline. The coupling unit is also configured to generate a first signal based on amplifying the communication signal according to a first winding ratio of the at least one transformer and a second signal based on attenuating the communication signal according to a second winding ratio of the transformer. The signal processing circuitry is configured to process the first signal and the second signal. The wireline is optionally a powerline.

BACKGROUND

1. Technical Field

This invention relates generally to the field of wireline communicationsand more particularly to coupling of signal processing circuitry with awireline communications medium.

2. Related Art

In communications systems, a communication signal may be received from awireline. The communication signal is typically an electromagneticsignal generated to transmit information or data. The wireline may beany physical medium configured to carry a signal such as a wire, atwisted pair cable, a coaxial cable, an electrical cable, or the like.The wireline may include a plain old telephone service (POTS) line, aDigital Subscriber Line (DSL), an Asymmetric Digital Subscriber Line(ADSL), an Ethernet line, or a powerline. The wireline transmits manysignals having varying characteristics. For example, signals may bewithin various frequency bands or of varying strengths. The wireline mayalso transmit a power signal which is not a communication signal,because the power signal may not transmit information or data.

The range of signal strengths depends on the strength and position of atransmitter, impedance, and noise on the wireline. For example, in apowerline, the range of signal strengths varies from the maximumallowable injected power to the noise floor. To illustrate, in the 1-30MHz band, the maximum allowable injected power is approximately −50dBm/Hz while the noise floor is approximately −150 dBm/Hz. This resultsin an overall input dynamic range of about 90 dB. Circuitry that isconfigured to receive a relatively large signal is typically less adeptat processing small signals and vice-versa. There is, therefore, atrade-off between detecting a large dynamic range of communicationsignals and detection sensitivity.

FIG. 1 illustrates a communications system 100 for processing acommunication signal in the prior art. In the communications system 100,a coupling unit transfers the communication signal from a wireline input102 from to signal processing circuitry. The coupling unit may include afirst filter 104 and a single ratio transformer 106. The first filter104 and the single ratio transformer 106 isolate the signal processingcircuitry and transform the voltage of the received communication signalto prevent damage to the signal processing circuitry. The single ratiotransformer 106 is a transformer having a single winding ratio between aprimary coil and a secondary coil. The winding ratio is the ratio of thenumber of windings between the primary coil and the secondary coil, anddictates the voltage gain or attenuation of the received communicationsignal by the single ratio transformer 106. A second filter 108 filtersthe signal output from the single ratio transformer 106.

A transformer having a single winding ratio, such as single ratiotransformer 106, will always produce an output signal having a fixedmagnitude ratio relative to the received signal. As a result, the signalprocessing circuitry following the transformer must be configured toreceive signals of a wide range in magnitudes, or distortions may occur.Input signals that are too large may be clipped while input signals thatare too small may be indistinguishable from a noise level.

To accommodate the variation in signal magnitudes as may be receivedfrom the single ratio transformer 106, some systems include variablecircuitry after the single ratio transformer 106. For example, aprogrammable gain stage, such as a single input active programmable gainamplifier (PGA) 110, can be used to amplify or attenuate signals into arange preferred by an analog to digital converter (ADC) 114. As theprogrammable gain stage typically uses active components to amplify thesignal, the programmable gain stage contributes to signal distortion, islimited by a noise floor, and is subject to signal magnitude offsets.Further filters, such as third filter 112, may be used to remove noisefrom the signal due to amplification by the PGA 110.

Typically, an Automatic Gain Control (AGC) system 116 is used to controlthe PGA 110 through a feedback loop 118. The ADC 114 outputs a digitalsignal at digital signal output 120. The digital signal may berepresentative of the received communication signal.

SUMMARY

While a variable gain stage provides some improvement in the input rangeof a communications system, there are still trade-offs betweenmaximizing signal-to-noise ratios and minimizing distortion of largesignals. There is, therefore, a need for improved systems and methods ofreceiving communication signals from a wireline.

In various embodiments, a transformer is provided to transform thelargest signal that can be present on the wireline into the largestsignal that the signal processing circuitry can receive without damage.In other embodiments, a transformer is provided to transform signalspresent on the wireline such that signals of low magnitude can bedetected over noise levels. Because of the wide range of signalmagnitudes that may be input to the transformer, the signals may need tobe selectively amplified or attenuated depending upon their magnitudes.

Various embodiments of the invention include systems and methods forprocessing a communication signal from a wireline. These systemscomprise a coupling unit and signal processing circuitry. The couplingunit may be configured to generate a plurality of output signals, havingdifferent magnitudes, from a single input signal. This plurality ofoutput signals may be generated using a transformer having a pluralityof winding ratios. For example, the coupling unit may be configured togenerate a first signal based on amplifying or attenuating acommunication signal using a first winding ratio of the transformer, andto generate a second signal based on amplifying or attenuating thecommunication signal using a second winding ratio of the transformer.The signal processing circuitry processes at least one of the firstsignal and the second signal depending on which of these signals bestmatches the input voltage range of the signal processing circuitry. Insome embodiments, the coupling unit is configured to communicate thecommunication signal in a first frequency band and a second frequencyband. The coupling unit may be configured to transmit a secondcommunication signal via the wireline. The wireline may include a firstmedium and a second medium. The first winding ratio may receive a firstpart of the communication signal from the first medium, and the secondwinding ratio may receive a second part of the communication signal fromthe second medium.

The first winding ratio and the second winding ratio may be establishedthrough a variety of approaches. For example, in some embodiments, thetransformer comprises a secondary coil having at least a first tap and asecond tap configured to transmit and receive signals according to firstand second winding ratios, respectively. In some embodiments, thetransformer comprises two separate secondary coils configured totransmit signals according to first and second winding ratios,respectively. In some embodiments, the transformer comprises a firsttransformer having a first winding ratio and a second transformer havinga second winding ratio.

In some embodiments, the signal processing circuitry comprises aprogrammable gain amplifier including two input stages configured toprovide different gain. For example, the signal processing circuitry maycomprise a first gain input stage configured to receive the first signaland a second gain input stage configured to receive the second signal.The first gain input stage may have a greater gain than the second gaininput stage. An automatic gain control system may be configured tocontrol the programmable gain amplifier and a selection of either thefirst signal or the second signal.

Various embodiments include a method for processing a communicationsignal from a wireline. The method comprises receiving the communicationsignal from a wireline into a coupling unit comprising a transformer;generating, in the coupling unit, a first signal based on amplifying orattenuating the communication signal from a first winding ratio of thetransformer; and generating, in the coupling unit, a second signal basedon amplifying or attenuating the communication signal from a secondwinding ratio of the transformer. The method also includes, in signalprocessing circuitry, processing the first signal and the second signal.In some embodiments, the wireline includes a powerline. The method mayalso include outputting the first signal at a first tap of a secondarycoil, and outputting the second signal at a second tap of the secondarycoil.

Various embodiments include a system for processing a communicationsignal from a wireline, the system comprising a coupling unit includingat least one transformer and configured to receive the communicationsignal from the wireline, to generate a first signal based on amplifyingthe communication signal from a first winding ratio of the at least onetransformer, and to generate a second signal according to a secondwinding ratio of the at least one transformer. The system also comprisessignal processing circuitry configured to process the first signal andthe second signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a prior art system for processing acommunication signal.

FIG. 2 is an illustration of a system configured for processing acommunication signal from a wireline in exemplary embodiments of theinvention.

FIG. 3 depicts alternative embodiments of the system of FIG. 2 includinga programmable gain amplifier.

FIG. 4 depicts alternative embodiments of the system of FIG. 2 includinga feedback path.

FIG. 5 depicts alternative embodiments of the system of FIG. 2 includinga plurality of switches.

FIG. 6 depicts alternative embodiments of a subsystem including avoltage source and switches that are provided as an alternative to theswitches of the system of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

A system for processing a communication signal from a wireline includesa coupling unit and signal processing circuitry. The coupling unitcomprises at least one transformer configured to receive thecommunication signal from the wireline and to generate at least twosignals. The signal processing circuitry is configured to process thetwo signals.

In some embodiments, by generating a first signal and a second signal,the system can handle a wider range of received communication signals,having greater variations in magnitude, relative to what is possible inthe prior art. This may be accomplished by generating the first signaland the second signal such that the first signal and the second signalhave different magnitudes relative to one another. For example, thesystem may be able to handle receiving relatively large communicationsignals without causing signal distortion, such as clipping, or damageto the signal processing circuitry. At the same time, the system mayhandle receiving relatively small communication signals without losingthe signals due to a noise floor. The system may be used in a modem chipcomprising low-voltage CMOS, wherein possible voltage and current rangesare limited.

FIG. 2 is an illustration of a system 200 configured for processing acommunication signal from a wireline 202 in exemplary embodiments of theinvention. The system 200 includes a coupling unit 204 and signalprocessing circuitry 222. In some embodiments, communication signals ofa variety of magnitudes may be received via wireline 202. For example,signals of 10 volts peak-to-peak (V_(p-p)) and signals of 2.5 V_(p-p)may both be received by coupling unit 210 via the wireline 202.

The coupling unit 204 comprises a transformer 206 configured totransform communication signals of various magnitudes received fromwireline 202 such that the communication signals can be processed usingthe signal processing circuitry 222. The signal processing circuitry 222may be configured to help extract transmitted information or data fromthe communication signal received from the wireline 202 by processingthe signal from the coupling unit 204. Variations in the magnitudes ofthe communication signals may be due to the strength and position of atransmitter, impedance of the wireline 202, noise on the wireline 202,and/or the like. A filter, not shown, may optionally be disposed betweenthe wireline 202 and the transformer 206 to filter the communicationsignals.

The transformer 206 is configured to generate two or more output signalsusing windings having two or more different winding ratios. A windingratio is the number of windings in a secondary coil 210 as compared tothe number of windings in a primary coil 208. The winding ratiodetermines the ratio of the voltage or current output from thetransformer 206 relative to the received input. For example, a windingratio of 2:5 (secondary to primary) will result in the output signalmagnitude being reduced to two-fifths of the received signal magnitude.The transformer 206 generates a first signal based on amplifying orattenuating the received communication signal according to a firstwinding ratio of the transformer 206. The transformer 206 also generatesa second signal based on amplifying or attenuating the receivedcommunication signal according to a second winding ratio of thetransformer 206.

In various embodiments, the two or more different winding ratios areestablished using a variety of approaches. For example, the transformer206 may comprise one secondary coil 210 having one or more taps asdepicted in FIG. 2. As illustrated, secondary coil 210 includes taps 212a, 212 b, 214 a, 214 b, and 216. The effective winding ratio isdetermined by the chosen taps of the secondary coil 210.

Alternatively, the transformer 206 may include a first secondary coilfor amplifying the communication signal according to a first windingratio and a second secondary coil for attenuating the communicationsignal according to a second winding ratio. In other embodiments, thetransformer 206 may comprise a first transformer having the firstwinding ratio and a second transformer having the second winding ratio.

In FIG. 2, the winding ratio is indicated by a number next to theprimary coil 208 (“5”) and the numbers next to the secondary coil 210(“3” or “1”). For example, the overall winding ratio of the secondarycoil 210 to the primary coil 208 in the embodiment shown is (3+1+1+3):5or 8:5. The magnitude of an output signal sampled at the outer outputs(taps 212 a and 212 b) of the full secondary coil will be 8/5^(ths) ofthe input signal to the transformer 206. Likewise, between the inneroutputs (taps 214 a and 214 b) of the secondary coil, the winding ratiois 2:5 and the magnitude of the output signal will be 2/5^(ths) of theinput signal. The amount of voltage gain or attenuation of thecommunication signal may further depend on the core material of thetransformer 206, the location of a tap, the frequency of thecommunication signal, and/or the cross-sectional area of the corematerial.

An amplified communication signal generated at the taps 212 a and 212 bis referred to herein as the “first gain signal.” Circuitry along whichthe first gain signal travels is referred to as the “first gain path.”Likewise, a communication signal generated at the taps 214 a and 214 bis referred to herein as the “second gain signal.” Circuitry along whichthe second gain signal travels is referred to as the “second gain path.”In some embodiments, the center tap 216 may be coupled with electricalground (0 V) to cause the amplitudes of the first gain signal and thesecond gain signal to be centered about 0 V.

In some embodiments, when a relatively small signal is received bycoupling unit 204, the signal is amplified using transformer 206 andprocessed using the first gain path. When a relatively large signal isreceived by coupling unit 204, the signal is attenuated usingtransformer 206 and processed using the second gain path. For example,if a 10 V_(p-p) signal is received from wireline 202, this signal may betransformed by a ratio of 2/5^(ths) to 4 V_(p-p) at taps 214 a and 214 band processed using the second gain path. If a 2.5 V_(p-p) signal isreceived from wireline 202, this signal may be transformed by a ratio of8/5^(ths) to 4 V_(p-p) at taps 212 a and 212 b and processed using thefirst gain path. These winding ratios are for illustrative purposesonly. Other winding ratios may be included in alternative embodiments.

In the embodiment shown in FIG. 2, the second gain path corresponds to awinding ratio of 2:5. In one example, a 10 V_(p-p) communication signalis stepped down to a 4 V_(p-p) second gain signal, resulting in a gainof −8 dB. In various embodiments, the winding ratio between taps 214 aand 214 b is greater than 1:10, 2:10, 3:5, 1:2, 1:1, or 2:1. In otherembodiments, the winding ratio between taps 212 a and 212 b is less than10:1, 10:2, 5:3, 2:1, 1:1, or 1:2. Further, in some embodiments, thevariation in magnitude of the communication signals on the wireline 202may range from approximately 10 mV_(p-p) to 20 V_(p-p).

The first gain path and second gain path include an amplifier 228 and anamplifier 234, respectively, within the signal processing circuitry 222.Amplifier 228 is configured to produce a first output signal at signalprocessing circuitry output 230, while amplifier 234 is configured toproduce a second output signal at signal processing circuitry output236. In some embodiments, amplifiers 228 and 234 are configured toreceive input signals of similar magnitudes. For example, both amplifier228 and 234 may be configured to receive signals with magnitudes rangingbetween 0.4 and 4 V_(p-p). However, because of the different windingratios to which the amplifiers 228 and 234 are coupled, these amplifierinput ranges may correspond to a received communication signal range(from wireline 202) of 0.25 V_(p-p) to 2.5 V_(p-p) for amplifier 228 and1 V_(p-p) to 10 V_(p-p) for amplifier 234.

Therefore, amplifiers 228 and 234 may be used to process receivedcommunication signals with magnitudes within substantially differentvoltage ranges. This difference in processing ranges may be achievedusing a passive element (e.g., transformer 206). Typically, the use of apassive element to process received communication signals tends tointroduce less noise into the processed signal than an active element.

The coupling unit 204 may further include optional current limitingresistors 218 a, 218 b, 220 a, and/or 220 b. The optional currentlimiting resistors 218 a, 218 b, 220 a, and/or 220 b may be configuredto limit a voltage received by the signal processing circuitry 222. Theoptional current limiting resistors 218 a and 218 b may be coupled inseries with the input ports 226 a and 226 b of the amplifier 228, andmay also be coupled in with optional protection devices 224 a and 224 b,respectively. Likewise, the optional current limiting resistors 220 aand 220 b may be coupled in series with the input ports 232 a and 232 bof the amplifier 234, and may also be coupled with optional protectiondevices 224 c and 224 d, respectively. As illustrated, the optionalprotection devices 224 a-d are disposed within the signal processingcircuitry 222. Alternatively, any of the optional current limitingresistors and/or optional protection devices may be disposed within thecoupling unit 204, signal processing circuitry 222, or neither.

The protection devices 224 may protect the amplifiers 228 and 234 fromevents such as the discharge of a static charge or other extraordinaryevents. In one example, the protection devices 224 are configured toprotect the amplifiers 228 and 234 by clamping input voltages betweencertain values. When voltages from the secondary coil 210 exceed thesevalues, current may flow through the protection devices 224 and voltagemay be dropped across the current limiting resistors 218 and 220. Insome embodiments, the protection devices 224 comprise an electrostaticdischarge (ESD) diode, a transistor having a specified breakdownvoltage, or the like.

FIG. 3 depicts alternative embodiments of the system of FIG. 2 includinga programmable gain amplifier 326. As illustrated, system 300 includes acoupling unit 302, the programmable gain amplifier (PGA) 326, an analogto digital converter (ADC) 336, a digital automatic gain control logic(AGC) 340, and a digital demodulator 344. The coupling unit 302 may bean alternate embodiment of the coupling unit 204, described withreference to FIG. 2. Further, the PGA 326, ADC 336, AGC 340, and digitaldemodulator 344 may correspond to the signal processing circuitry 222,described with reference to FIG. 2. In various embodiments, the system300 is configured to receive an analog communication signal from thewireline 202, process the analog communication signal, and convert theanalog communication signal to a digital output signal at the digitaldemodulator output 346. The digital output signal may be processedfurther using, for example, CMOS or BiCMOS circuitry.

The coupling unit 302 includes a transformer 304 and an impulsive noiselimiting high pass filter 314. The transformer 304 may be an alternateembodiment of the transformer 206, described with reference to FIG. 2.The transformer 304 includes a primary coil 308, a core 306, and asecondary coil 312. The primary coil 308 is coupled to the wireline 202.The transformer 304 may optionally include a low frequency capacitor 310configured to reject low frequency noise, such as a 60 Hz power signal,from the wireline 202. In some examples, the low frequency capacitor 310may be of type Y1, Y2, X1, or X2 class. The secondary coil 312 of thetransformer 304 comprises a plurality of taps coupled to the impulsivenoise limiting high pass filter 314. The impulsive noise limiting highpass filter 314 includes a network of capacitors such as capacitors 316a, 316 b, 318 a, and 318 b and inductors such as inductors 320 a, 320 b,322 a, and 322 b coupled between the plurality of taps of the secondarycoil 312 and the PGA 326. The impulsive noise limiting high pass filter314 optionally further includes a direct current (DC) bias 324. Otherpassive filters may be included in the coupling unit 302 as will beapparent to those skilled in the art.

The PGA 326 comprises a low magnitude input signal amplifier 330, a highmagnitude input signal amplifier 334, and an optional final amplifierstage 336. The low magnitude input signal amplifier 330 is optionallyconfigured to receive signals of lower magnitude than the high magnitudeinput signal amplifier 334. For example, the low magnitude input signalamplifier 330 may be configured to process (e.g., amplify) a first gainsignal received from the outer taps of the secondary coil 312. Likewise,the high magnitude input signal amplifier 334 may be configured toprocess the second gain signal received from the inner taps of thesecondary coil 312. In some embodiments, the low magnitude input signalamplifier 330 has a greater gain than the high magnitude input signalamplifier 334. The outputs of the low magnitude input signal amplifier330 and the high magnitude input signal amplifier 334 are provided tothe final amplifying stage 336.

The inputs 328 a and 328 b of the low magnitude input signal amplifier330 may be coupled with protection structures such as protection devices224 a and 224 b. Likewise, the inputs 332 a and 332 b of the highmagnitude input signal amplifier 334 may be coupled with protectionstructures such as protection devices 224 c and 224 d. The low magnitudeinput signal amplifier 330 and the high magnitude input signal amplifier334 are optionally embodiments of amplifiers 228 and 234, described withreference to FIG. 2. In some examples, the low magnitude input signalamplifier 330 and the high magnitude input signal amplifier 334 may havea fixed gain.

The final amplification stage 336 is configured to process signalsreceived from the low magnitude input signal amplifier 330 and the highmagnitude input signal amplifier 334. The signals may be processed suchthat a signal output from the final amplification stage 336 to the ADC336 is provided with a desired signal-to-noise ratio. For example, thedesired signal-to-noise ratio may be at least 30 dB. The desiredsignal-to-noise ratio may depend on the bit resolution of the ADC 336.

The ADC 336 provides feedback to the AGC 340 based on the output of thefinal amplification stage 336. The feedback is provided to form afeedback control loop with the PGA 326. The AGC 340 is configured togenerate control signals 342 a, 342 b, and 342 c. The control signals342 a, 342 b, and 342 c are used by the PGA 326 to control the lowmagnitude input signal amplifier 330, the high magnitude input signalamplifier 334, and/or the final amplification stage 336, respectively.The control signals 342 a and 342 b may be used to ensure that the finalamplification stage 336 receives input signals from only one of the lowmagnitude input signal amplifier 330 and the high magnitude input signalamplifier 334. The control signals 342 a, 342 b, and 342 c may also beused to control the gain of the low magnitude input signal amplifier330, the high magnitude input signal amplifier 334, and the finalamplification stage 336, respectively.

The ADC 336, which may comprise a pipeline ADC, may be configured toconvert a communication signal having the desired signal-to-noise ratioto a digital signal. The ADC 336 may output the digital signal to thedigital demodulator 344. After the communication signal is converted tothe digital signal, the digital demodulator 344 demodulates the digitalsignal to extract digital information content and output the digitaloutput signal which may be further processed by other devices.

FIG. 4 depicts alternative embodiments of the system of FIG. 2 includinga feedback path. Signals from wireline 202 may be received by a firstfilter 402. The first filter 402 may be configured to separatecommunication signals from other signals carried by the wireline 202.For example, a high frequency communication signal may be separated fromone or more low frequency signals, such as a 60 Hz power signal.

The system 400 includes a coupling unit 404 which receives input fromthe first filter 402. The coupling unit 404 may be an alternateembodiment of the coupling unit 204 or the coupling unit 302, describedwith reference to FIGS. 2 and 3. The coupling unit 404 includes atransformer 406 having more than one winding ratio. The transformer 406may be an alternate embodiment of the transformer 206 or 304, describedwith reference to FIGS. 2 and 3. The coupling unit 404 may furtherinclude one or more filters, such as second filter 408 and third filter410. The second filter 408 and third filter 410 may filter one or moresignals output from one or more secondary coils of transformer 406. Insome examples, the second filter 408 and third filter 410 may includehigh pass filters.

The system 400 may include alternative embodiments of signal processingcircuitry 222 (described with reference to FIG. 2) which may include amultiple input active programmable gain amplifier (PGA) 412, a fourthfilter 414, an analog to digital converter (ADC) 416, and an automaticgain control (AGC) 418. The PGA 412 is optionally configured to processa communication signal received from the coupling unit 404 such that thecommunication signal has a signal-to-noise ratio of at least 30 dB, forexample. The PGA 412 may be controlled using feedback 420 provided bythe AGC 418. The fourth filter 414 may be configured to filter a signalreceived from the PGA 412. The ADC 416 may be configured to convert thefiltered analog communication signal to a digital output signal atdigital signal output 422. The ADC 416 may also generate a signal thatis processed by the AGC 418 to generate the feedback 420 to the PGA 412.In various embodiments, the first filter 402, the second filter 408, thethird filter 410, and/or the fourth filter 414 include analog signalprocessing circuitry. Some embodiments include a separate instance ofADC 416 for each of the first gain path and the second gain path.

FIG. 5 depicts alternative embodiments of the system of FIG. 2 includinga plurality of switches. The system 500 includes signal processingcircuitry 510 configured to generate a first output signal at firstsignal processing circuitry output 540 from a first gain path and asecond output signal at second signal processing circuitry output 550from a second gain path. The signal processing circuitry 510 of system500 may be an alternate embodiment of the signal processing circuitry222 of system 200, further including a first gain switch 520 and asecond gain switch 530. The first gain switch 520 may be configured toshort circuit the inputs 226 a and 226 b of amplifier 228. The secondgain switch 530 may be configured to short circuit the inputs 232 a and232 b of amplifier 234. In some embodiments, only one of the first gainswitch 520 and the second gain switch 530 is open at a time. Thus, onlyone of amplifiers 228 and 234 may receive signals at the same time. Forexample, the first gain switch 520 may be closed to short circuit theinputs 226 a and 226 b of amplifier 228 when the amplifier 234 isactivated by the signal processing circuitry 510.

First gain switch 520 and second gain switch 530 may serve two purposes.The first purpose is that the first gain switch 520 and the second gainswitch 530 may protect the inputs of amplifiers 228 and 234 fromexcessively large signal magnitudes. For example, if a 10 V_(p-p) signalis received from wireline 202, a voltage across taps 212 a and 212 bwould include a signal of 16 V_(p-p) as a result of the winding ratio inthe embodiment of transformer 206 illustrated in FIG. 5. While this 10V_(p-p) voltage may substantially be prevented from reaching amplifier228 by protection devices 224 a and 224 b, if switch 520 were closed,switch 520 would reduce the required current carrying capacity ofprotection devices 224 a and 224 b. When switch 520 is closed, the 10V_(p-p) voltage would be dropped across current limiting resistors 218 aand 218 b.

The second purpose is that the first gain switch 520 and the second gainswitch 530 may be used to regulate the impedance load on the wireline202 that is caused by the system 500. For example, by choosingappropriate values of current limiting resistors 218 a, 218 b, 220 a,and 220 b, and using switches 520 and 530, a relatively constantimpedance load can be maintained on the wireline 202 even when theoutput of secondary coil 210 is sampled using different taps such as 212a and 212 b or 214 a and 214 b. In some embodiments, the values ofcurrent limiting resistors 218 a, 218 b, 220 a, and 220 b are configuredsuch that the ratio of the resistance between the current limitingresistors 218 a and 218 b and the current limiting resistors 220 a and220 b is the square of the ratio of windings between the first gain pathand the second gain path. For example, if the ratio of windings betweenthe first gain path and the second gain path is 8:2, as in FIG. 5, theratio of the resistances of current limiting resistors 218 a and 218 band current limiting resistors 220 a and 220 b may be 16:1.

Switches 520 and 530 may be optionally controlled by a feedback signal(not shown) received from other elements of system 500. For example, thefeedback signal may be received from embodiments of PGA 412, ADC 418, orAGC 418. If a signal is being processed using amplifier 228 via thefirst gain path, and a system element providing feedback determines thatthe signal being received or input to the amplifier 228 is too large forthe amplifier 228 to process, then the feedback signal is used to closeswitch 520 and open switch 530 such that the second gain path isactivated and the signal can be processed using amplifier 234. A similarprocess may occur when the signal received is too small for amplifier234 to process.

FIG. 6 depicts alternative embodiments of a subsystem 600 including avoltage source 630 and switches 610 and 620 that are provided as analternative to the switches 520 and 530 of the system of FIG. 5. Thesubsystem 600 replaces the amplifier 228 and switch 520 of the system500 illustrated in FIG. 5. The subsystem 600 may also replace theamplifier 234 and switch 530 of the system 500 illustrated in FIG. 5.The subsystem 600 enables an input signal voltage to the amplifier 228to be controlled. For example, if the signal voltage level from couplingunit 204 is offset and/or AC-coupled, the voltage source 630 can be usedto control the signal voltage level from the coupling unit 204. Theinputs 226 a and 226 b of the amplifier 228 are connected to theelectrostatic discharge devices 224 a and 224 b. The switch 610 isconnected between the input 226 a of the amplifier 228 and the voltagesource 630. Likewise, the switch 620 may be connected between the input226 b of the amplifier 228 and the voltage source 630. The switches 610and 620 control a connection to the voltage source 630 which may be usedto clamp an input signal to the amplifier 228 to within a specifiedvoltage range. For example, the switches 610 and 620 may be configuredto clamp the inputs 226 a and 226 b of the amplifier 228 to a voltage ofthe voltage source 630 if the signal processing circuitry 510 activatesthe amplifier 234 (described with reference to FIG. 5). The voltagesource 630 may include, for example, a power rail, an op-amp, or thelike.

Several embodiments are specifically illustrated and/or describedherein. However, it will be appreciated that modifications andvariations are covered by the above teachings and within the scope ofthe appended claims without departing from the spirit and intended scopethereof. For example, transformer 206 may be configured to include morethan two winding ratios. In a half duplex communication protocol, onewinding ratio may be used for transmission and another winding ratio orboth winding ratios may be used for reception. Some windings may be usedfor both transmission and reception. In other examples, the transformer206 may be used for both transmission and reception of signals. In someembodiments, the signal passes through media such as telephone linesand/or coaxial cable in addition to or instead of the power line. Insome embodiments, the transformer 206 is used for communication in morethan one frequency band. For example, the transformer 206 may transmit asignal in a first frequency band and receive a separate signal in asecond frequency band. In some embodiments, there may be othercomponents in parallel to or in series with embodiments of the presentinvention, the other components configured to filter or conditionsignals. Amplification of a signal may also include attenuation of thesignal, or amplification by a negative amplification factor. Anamplifier may also provide unity gain.

The embodiments discussed herein are illustrative of the presentinvention. As these embodiments of the present invention are describedwith reference to illustrations, various modifications or adaptations ofthe methods and or specific structures described may become apparent tothose skilled in the art. All such modifications, adaptations, orvariations that rely upon the teachings of the present invention, andthrough which these teachings have advanced the art, are considered tobe within the spirit and scope of the present invention. Hence, thesedescriptions and drawings should not be considered in a limiting sense,as it is understood that the present invention is in no way limited toonly the embodiments illustrated.

1. A system for processing a communication signal from a wireline, thesystem comprising: a coupling unit comprising at least one transformerand configured to receive the communication signal from the wireline, togenerate a first signal based on amplifying the communication signalfrom a first winding ratio of the at least one transformer, and togenerate a second signal according to a second winding ratio of the atleast one transformer; and signal processing circuitry configured toprocess the first signal and the second signal; wherein the signalprocessing circuitry comprises a programmable gain amplifier, theprogrammable gain amplifier comprising a first gain input stageconfigured to receive the first signal and a second gain input stageconfigured to receive the second signal.
 2. The system of claim 1,wherein the at least one transformer comprises a secondary coilcomprising at least two taps, the at least two taps configured to bothtransmit and receive a signal according to a winding ratio correspondingto the respective taps.
 3. The system of claim 1, wherein the couplingunit is configured to communicate the communication signal in a firstfrequency band and a second frequency band.
 4. The system of claim 1,wherein the at least one transformer comprises a first secondary coilincluding the first winding ratio and a second secondary coil includingthe second winding ratio.
 5. The system of claim 1, wherein the at leastone transformer comprises a first transformer having the first windingratio and a second transformer having the second winding ratio.
 6. Thesystem of claim 1, further comprising an automatic gain control systemconfigured to control the programmable gain amplifier and a selection ofeither the first signal or the second signal.
 7. The system of claim 1,wherein the coupling unit further comprises at least one series resistorconfigured to limit a voltage received by the signal processingcircuitry in conjunction with shorting, clamping, or protectionstructures.
 8. The system of claim 7, wherein the signal processingcircuitry further comprises at least one switch configured to shortcircuit a first input stage of the signal processing circuitry if thesignal processing circuitry activates a second input stage of the signalprocessing circuitry.
 9. The system of claim 7, wherein the signalprocessing circuitry further comprises at least one switch configured toclamp a first input stage of the signal processing circuitry if thesignal processing circuitry activates a second input stage of the signalprocessing circuitry.
 10. The system of claim 1, wherein the firstwinding ratio is configured to amplify the communication signal by apositive amplification factor and the second winding ratio is configuredto attenuate the communication signal.
 11. The system of claim 1,wherein the coupling unit is configured to transmit a secondcommunication signal via the wireline.
 12. The system of claim 1,wherein the wire line comprises a powerline.
 13. The system of claim 1,wherein the wireline comprises a telephone line.
 14. The system of claim1, wherein the wire line comprises a coaxial cable.
 15. The system ofclaim 1, wherein the wireline includes a first medium and a secondmedium, the first winding ratio configured to receive a first part ofthe communication signal from the first medium and the second windingratio configured to receive a second part of the communication signalfrom the second medium.
 16. A method for processing a communicationsignal from a wireline, the method comprising: receiving thecommunication signal from a wireline at a coupling unit comprising atleast one transformer; in the coupling unit, generating a first signalbased on amplifying or attenuating the communication signal using afirst winding ratio of the at least one transformer; in the couplingunit, generating a second signal based on amplifying or attenuating thecommunication signal using a second winding ratio of the at least onetransformer; and processing the first signal and the second signal insignal processing circuitry, the processing including: processing thefirst signal at a first gain input stage in a programmable gainamplifier, and processing the second signal at a second gain input stagein a programmable gain amplifier.
 17. The method of claim 16, whereinthe wire line comprises a power line.
 18. The method of claim 16,further comprising: outputting the first signal at a first tap of asecondary coil; and outputting the second signal at a second tap of thesecondary coil.
 19. The method of claim 16, wherein the at least onetransformer comprises a first secondary coil including the first windingratio and a second secondary coil including the second winding ratio.20. The method of claim 16, wherein the at least one transformercomprises a first transformer having the first winding ratio and asecond transformer having the second winding ratio.
 21. The method ofclaim 16, further comprising controlling the programmable gain amplifierusing an automatic gain control system.
 22. The method of claim 16,wherein the processing further comprises activating a first gain pathand short circuiting a second gain path.
 23. The method of claim 16,wherein the first signal has a larger peak-to-peak voltage than thesecond signal.